Motorised vehicles are well known for use in material handling that carry an implement and have a hydraulically operated lifting arm for moving the implement. Examples of such vehicles are tractors, loaders e.g. compact wheel loaders, backhoes, excavators and forklifts.
All of such vehicles are often used to perform repetitive tasks where the hydraulically operated implement is required to return to a starting position or state. For example, in the case of a loader, the lifting arm, which is formed may comprise a system of mutually pivoted limbs, is used to support a bucket that can be tilted and moved up and down with the aid of tilting and lifting hydraulic cylinders, respectively. If the loader is used, for example, to load material from a mound resting on flat ground onto a truck, at the commencement of each loading cycle, the bucket must adopt a horizontal attitude so that it can pick up material when the vehicle is driven forwards and it should rest on the ground under the action of its own weight, so as naturally to follow the contour of the ground. Once the bucket is full, it needs to be tilted so that material does not fall out of the bucket, positioned over the truck by moving the vehicle and rotating the lifting arm and then tilted to empty its contents into the truck.
Having discharged its load into the truck, the bucket has to be returned to the position for digging and lowered to rest on the ground under its own weight. These operations need to be performed at the same time as the operator is manoeuvring the vehicle to a new position in readiness for next loading cycle. The process can be simplified significantly by enabling the implement to return to a preselected dig position (referred to herein as a “return to dig” (RTD) functionality), and enabling the lifting arm to return to a free floating state (referred to herein as a “return to float” (RTF) functionality) without requiring intervention from the operator. It is clear from the previous that these functionalities also apply to forklifts.
The closest prior art to the present invention is believed to be US2002/0073833 which discloses a return to dig system for a work machine having at least one implement that is actuated by a hydraulic cylinder using a switch, such as with a push button, to control a valve and solenoid to move the implement from a remote position to a preselected position, usually the starting position. The preselected position is determined by a sensor and a detectable element, such as a magnet. When the detectable element is sensed, the solenoid is repositioned to stop movement of the implement. The push button is located on a joystick that controls the movement of the implement and various other functions of the work machine. The actuation of the return to dig system by the push button does not affect any other unrelated function of the work machine controlled by the device.